AI Confusion...

[F. Guffey]

That reflects Hatcher's experience adding headspace to 1903 Springfields up until the point the cases started cracking as the cartridge was held in place by the extractor claw.

Clark,

If H&H was going to make chambes "generous" for reliability in bad conditions with qestionable ammunition, then the belt makes more sense. The Lee-Enfields were known to have "generous chambers" for reliability and headspaced on the rim.

Still, a mauser action would let the round fire even with excessive headspace without a rim to stop the firing pin push forward.

Jimro, I have always said a very boring story, for me, always starts with "Hatcher said", when Hatcher is quoted and the subject of the 03 is "THE RIFLE" I always ask "Where are all the 03 experts?" Then there is the claim he advanced the reamer until the chamber did not have a shoulder. There was nothing to gain by moving the shoulder forward. It is claimed he moved the shoulder forward .080", if there was any truth in the head space and case head separation .080" would have been more than enough.

Again, I have fired 8mm57 ammo in a 8mm06 chamber, head space??? The difference in length from the shoulder to the bolt face of an 8mm/06 chamber and the length of an 8mm57 case from the shoulder to the case head is .127". We all know? a case will not stretch .080" between the case head and case body, we should all know the case will not stretch .127" between the case head and case body.

The assumption, the case stretches between the case head and case body, that story should start with "Once upon a time" as in it just does not happen. I suggested reloaders to scribe the case at the case body/shoulder juncture, I did, the line did not move, if there was any truth the bullet, case and powder running forward to avoid the firing pin strike the shoulder and neck would be forced forward and the neck would be the same length.

Back to the 8mm57 fired in the 8mm06 chamber, the cases were ejected with very short necks and long case bodies, the scribed line at the case body/shoulder juncture did not move, it was at the same place, part of the neck of the case became part of the shoulder and part of the shoulder became part of the case body.

It made more sense for the Hatcher wildcat chamber to be cut in a M1917. Hatcher and the wildcat, I refer to the chamber as the 30/06 Hatcher +.080" Wildcat chamber, he became a wildcatter and a fire former without case head separation.

And again, I ask about the 03 experts, a friend built magnificent wildcat rifles from variations of the 03. he had 5 out of 10 case head separations. I informed him I could have fixed the problem before he left the shop, I informed him I could have determined the possibility the rifle had the tendency to have case head separation when fire forming, then I told him I could have met him at the range and fix the problem long enough for him to fire form his cases, I am not the 03 expert.

F. Guffey

[Jimro]

F. Guffey,

The rounds I was shooting were Winchester commercial loaded with nickel cases. And yes, the cases separated, in the same spot each time, as I went through half a box of ammo. God loves young boys and fools, for he surely made enough of us.

I've also heard the stories of the folks who touched off 7.62x51 in a 30-06 Garand chamber and have the "rimless 45-70" get ejected.

What I think happened in my case is that the nickel plating changed the coefficient of friction with the chamber wall enough to allow the brass to slide and stretch then fail instead of "gripping" the chamber wall and blowing the shoulder out and forward.

Can't really prove that is exactly what happened, but it happened, and I've always double checked my headspace depth calculations when shortening a long chambered barrel ever since.

Jimro

[F. Guffey]

I've also heard the stories of the folks who touched off 7.62x51 in a 30-06 Garand chamber and have the "rimless 45-70" get ejected.

The Garand is not the rifle a shooter/reloader wants to feed cases that are short from the shoulder to the case head. When the 308W is fired in the M1 Garand the shooter is not driving faster that their guardian Angle can fly.
The 308 W head spaces on the case body juncture of the case, the 30/06 chamber is smaller in diameter by at least .011", meaning the 308W head spaces on the case body/shoulder juncture. Cases are ejected with very short shoulders. When the 308W is chambered in a 30/06 chamber the case body is sized.

If there was a 'nice thing about that' it would be low pressure.

I do not know what rifle you were shooting when you had case head separation.

F. Guffey

[Jimro]

It was a Turk K.Kale m98 action, rem 700 takeoff barrel that was supposedly "short chambered" by the converter but came cut way too deep.

Every round chambered went "boom" and every piece of brass cracked.

Jimro

[James K]

I have fired a number of 7.62 NATO rounds in an unmodified .30 M1 rifle. I do not recommend firing any cartridge in a rifle not chambered for it, but there appears to be no danger in doing so in this case. As noted, the powerful operating rod spring of the M1 wedges the shorter cartridge into the chamber. While it is not "headspaced" in any real sense, firing, extraction, and ejection are normal. Extraction without firing, however, is very difficult. The fired case does look like a rimless .45-70.

So, it is not a recommended practice, but it could be done in an emergency without danger.

Jim

[F. Guffey]

Every round chambered went "boom" and every piece of brass cracked.

Forgive, cracked where? I built a rifle and went to the range with the new owner. He was doing everything he could to close the bolt with no success, he attempted to chamber a round by push feed. I managed to get the extractor to jump the rim by compressing the bulged extractor against the bolt forcing the claw past the case rim.

The action was a control feed 98 Mauser model 98, the fact ammo could not be push fed assured me the firing pin was not going to force the bullet, case and powder forward in an attempt to avoid the primer strike until the shoulder of the case collided with the shoulder of the chamber. With a long chamber he could have managed to close the bolt allowing the case to jump the extractor after the case expanded and locked onto the chamber. Under those conditions I would expect the case to stretch between the case head and case body.

I cut the chamber, I formed the cases to fit the chamber. Back to 03 experts, a few know the 03 was designed with a lock out that allows for push feed instead of control feed. My friend built 5 magnificent wildcats, he had case head separation etc. he could have formed cases to fit before going to the range.

F. Guffey

[Bart B.]

I've seen dozens of 7.62 NATO empty cases ejected from .30 caliber Garands. A few times, the guy shooting them had no idea he had a .30 caliber Garand until his scorer mentioned it to him. He assumed that because the USN had converted all their match grade Garands to 7.62 NATO as well as those used at the San Diego boot camp range, all the ones from other ship and station armories would also be the NATO version.

A few had shot 10 rounds standing, 10 in sitting rapid fire at two different ranges before someone clued them in. The match directors finally got the man issuing ammo at the matches to check competitors' rifles before issuing them ammo. This happened at both USN and USAF rifle matches back in the late '60's and early '70's.

[Jimro]

F. Guffey,

This picture of slamfires shows the same spot the brass cracked for me: http://smg.photobucket.com/user/Slam...8d9f3.jpg.html

Although I was shooting commercial winchester ammunition.

Jimro

[James K]

Those cases show the type of separation typical of excess headspace. However, there may be more to it than that, because one case shows a problem in the case neck, possibly due to season cracking or to acid in the powder causing brass deterioration over long storage.

Jim

[std7mag]

Me thinks I've been thread jacked....

[Jimro]

James K,

I didn't take pictures of the Winchester commercial ammo that failed, at the time I didn't even bother owning a cell phone that I could use to snap a photo. So I just searched for the photo that was closest to what I saw, a semi jagged crack about a thumbswidth from the case head.

Obviously I don't know the full story behind slamfires ammunition, but I think acid corrosion played a part too.

Jimro

[F. Guffey]

Me thinks I've been thread jacked....

Forgive me for my part. You have an investment in tools and parts, before I start I determine the starting point and finishing point, Confusing, the part where it is claimed the go-gage for one chamber is the no go-gage for the other. The measure from for the 308 W family of chambers is .400", problem, the case body for the Ackley chamber is longer than the standard 308, the shoulder angle is greater, this causes the neck on the Ackley to be longer. In theory the shoulder pivots on the .400" datum, not exact.

Three different Ackley chamber for the same chamber. In the perfect world the builder would start with a new barrel, next, it is best to move the barrel back, how much and method for deterring. Again, the Ackley reamer will not clean up the old chamber because of the long case body and longer neck, so the person reaming the chamber must determine the amount of barrel set back. SET BACK, setting the barrel back one turn will require cutting the face of the barrel.

Last and not uncommon, ream the chamber, disregard cleaning up the shoulder/neck juncture. The part of the chamber that is not removed will not allow the builder to fire form cases because the case will not head space on the new shoulder but part of the old shoulder. Meaning when fire forming the short neck of the parent case will not be sized down when chambered.

If when fire forming the case takes off for the front of the chamber, the case head could separate. I have very few rifles that will allow the case to take off and avoid the primer strike, that said, I am a case former, there is no excuse for me to chamber a case that that does not fit the chamber from the shoulder of the chamber and the bolt face.

With your 7MM08, before I started with the Ackley reamer I would determine the length of the chamber from the shoulder to the bolt face. I do not need a head space gage because I know the go-gage will allow the bolt to close.

Back to measure from and datum. I form 30/06 cases to 308 W cases. When forming 308 W cases I form a new shoulder that is shorter than the 30/06 by .388", All I have to know is when to stop forming the shoulder, I use a feeler gage to adjust the gap between the bottom of the die and top of the shell holder.

A reminder, do not punch a hole in the feeler gage. we are not trying to win the war, we are trying to determine the length of the chamber, so. We do not need to punch primers therefore it is not necessary and it is possible to start with cases that do not have primers.. There is nothing like starting with new cases, when forming cases a reloader does not want to find out the cases he is forming will not behave. After determining the length of the chamber the formed case can be thrown away, of saved for future reference.

Forming dies, If I had one forming die it would be the 308W case forming die, If I had two the other would be the 243W forming die, the third? It would be the 7MM08. I have 15 forming dies, I do not have the 7mm08 forming die.

F. Guffey

[Bart B.]

Jimro:

What I think happened in my case is that the nickel plating changed the coefficient of friction with the chamber wall enough to allow the brass to slide and stretch then fail instead of "gripping" the chamber wall and blowing the shoulder out and forward.

When folks bought Federal nickel plated .308 cases for matches, they started loading them with reduced charges they had used in their Winchester and Remington cases for short range matches. Those slippery nickel ones slid further forward from firing pin impact setting their shoulder back quite a bit (some I've measured got set back .005" or more). Oft times, the back half of the case didn't get stretched back enough to have their head stop against the bolt face. Their fired primers stuck out past the bolt face several thousandths.

It's the thicker back end of the case that gets blown backwards as the thinner front half of the body starts to grip the chamber wall. Their shoulder's hard against the chamber shoulder from firing pin impact when the round fires and stays there while the case expands starting at the shoulder and works its way back towards the pressure ring.

In spite of having about .003" head clearance in the chamber when new, unless they were resized properly in a full length sizing die that moved their shoulders forward to where they were when new, incipient head separation soon followed and a few had head separation. Some protruding primers in such cases stuck out almost .010 inch. Adding a grain or two of powder to the reduced loads cured this problem. It happened to me.

[Unclenick]

Back On Topic:

Std7mag,

I think Dave Manson's write-up tells you what you need to know. Since only about 0.004" of setback is required, and if your barrel doesn't have a fixed sight on it that needs to be turned in a full 360° to come back to top dead center, I doubt you'll have to clean the barrel face back 0.003-0.004". You'll probably have that much wiggle room already. I believe all the Savage/Stevens barrels have 20 TPI threads, so about 1/12 or 1/3 of 1/4 of a full turn (30°) will get you that much closer. You can just mark the barrel with a pencil or masking tape to work that out.

On the other hand, I believe the AI gauges should have AI shoulder angle on them and therefore not be the same as a .308 gauge. That part of the description has me perplexed.

Assuming the AI shoulder angle is on the gauge, if you are reaming by hand, paint the inside of the existing chamber with Magic marker or layout die, then ream until a flashlight shows you the shoulder of the original chamber is starting to clean up. It should start at the outside and clean up moving inward unit the cleaning meets the neck last. Just go slowly until that last little bit of ink just comes off that inside corner with the neck. That will be the minimum material removal.

You can leave the recoil lug off for this: Screw the barrel into the gun with the bolt closed and keep going until you feel the barrel just meet the bolt. Use a pencil to make registration marks on the receiver and barrel threads. Unscrew the barrel and strip the bolt. Chamber the GO gauge with the stripped bolt (bolt head on, of course, but all the spring-operated parts gone to avoid pressure anywhere when closing the action). Gently screw the barrel back in. Ideally, it will meet the gauge before the registration marks have lined back up. That is, it needs to meet the gauge before it would meet the assembled bolt. However, if it stops at or beyond* the registration marks, then you will need to have some metal taken off the breech end of the barrel to get a fit. How much depends on how much rattle room is left for the gauge when you have the registration marks lined up. You can find this by putting shims under that gauge. You want that much, plus a little wiggle room taken off. Maybe an additional 0.005".

If it all fits and stops before the registration marks, or if you've set the breech end of the chamber back to make it so, you can put the recoil lug back on and reinstall the barrel using your GO gauge and stripped bolt, and you can check that the GO gauge goes and the NO-GO does not in order to meet the standard for a newly cut chamber. Being closer to GO than to NO-GO gives you the longest case life if you are also full length resizing. If you are resizing to match the chamber, it only makes a difference to the first firing.


*The extractor being out of the way can make this happen.



Back Off Topic, briefly.

Jimro,

Having seen neckless, wide-mouth, but otherwise intact .308 brass ejected from a .30-06 hunting rifle before, I'm wondering if the nickel plating you had embrittled or weakened your brass. I know I've seen mouth splits develop early in nickel plated pistol brass. Not all nickel plated brass cases do this. Some headstamps I've had just had their plating gradually wear off. But others definitely split early.

Some years ago I made the mistake of buying 500 nickel-plated Remington .308 cases, thinking it was an easy way to distinguish my service rifle brass from that of other competitors so I wouldn't have as much of it disappear at matches. I had it backwards. More of it disappeared. The white color reflects the color of grass with such fidelity as to make plated cases all but invisible on the ground. Anyway, I decided to relegate that lot of brass to field hunting loads. It has good weather resistance for a lengthy trip, and since I'm going to lose it anyway, I don't feel so bad about leaving it behind and don't have to worry about nickel flakes embedding in my dies.

[Jimro]

Back on topic,

The AI headspace datum is different than the parent cartridge but you should still be able to use the "Go" and "no go" guages of the parent cartridge as long as the shoulder angle on the guages is precisely ground down to the neck junction. Since the AI shoulder is sharper, the only point where the two angles will interesect is at the neck junction, not the original datum point for the parent cartridge.

Still, set the barrel back before cutting the AI chamber. Then set headspace again if needed, the barrel nut makes it easy to do.

Back off topic,

Bart B. I had over 0.040" of excess clearance, we are talking swallowing a field gauge oversized. The claw extractor held the brass against the bolt face as it should. I know that an in spec Mauser action has between 0.050 and 0.055 firing pin protrusion, however when the cartridge is held against the bolt face by the extractor, and stabilized from the side by the chamber wall, there is no way for that to push the shoulder forward hard into the chamber, mechanically it is impossible.

If the action had been push round feed I would have expected the snap over extractor to push the brass so far into the oversized chamber that the firing pin couldn't have lit off the primer, especially if the primer was below flush. Can't know for sure though, as I don't want to screw with a rifle enough to test that idea.

Unclenick,

I've wondered that too about the nickel plating, but since the problem went away when headspace was corrected I chalked it up to my own failure to measure correctly the first time.

Jimro

[F. Guffey]

Those slippery nickel ones slid further forward from firing pin impact setting their shoulder back quite a bit (some I've measured got set back .005" or more). Oft times, the back half of the case didn't get stretched back enough to have their head stop against the bolt face. Their fired primers stuck out past the bolt face several thousandths.

Bart B., I know, I am the only one that missed it so tell me again, how did you measure the cases that you claimed shortened when the firing pin hit the primer? I ask because I have killer firing pins, I have firing pins that crush the primer before the case, bullet and powder knows their little buddy the primer has been hit.

All of this stuff happens in a hurry, How big of a hurry? Time and events are measured in milliseconds. That is the reason I believe time is a factor.

I do not wonder. I have had crushed primers, I have had primers with neat dents, the dents were formed when the pressure inside the primer formed to the protruding firing pin (if the spring was strong enough to overcome the pressure, it is a .7854 thing).

F. Guffey

[Bart B.]

Mr. Guffey, I've told you several times before putting how I've measured that in several posts over the years in this forum. But it involves something you think is not a valid measurement, so that's why I think you don't plant it into memory; you forget about it because it, to you, is nonsensical.

With your claimed expertise in machine shop gunsmithing tools and practices, I would think it's easy figure out how much a case shoulder's set back from firing pin impact and not even shoot a bullet down their barrel.

Think about it; it's a before and after issue with a primed case.

[F. Guffey]

Mr. Guffey, I've told you several times before putting how I've measured that in several posts over the years in this forum.

Bart B., I know, I am the only one that missed it so tell me again, how did you measure the cases that you claimed shortened when the firing pin hit the primer?

There are claims a reloader can seat a primer into a minimum length/full length sized case, then chamber and then pull the trigger. It is claimed this method/technique can be used to determine the difference in length between the chamber from the shoulder to the bolt face and the length of the case from the shoulder to the head of the case SIMPLY by measuring the primer protrusion.

Stay with me, if that claim is true then your firing pin impact shorting the length of the case .005" from the shoulder to the case head causing a false reading when measuring the protruding primer. . Because of the protruding primer a reloader is going to adjust the die off the shell holder to prevent oversizing the case, and if you are keeping up it will be necessary to size the case with the bolt when chambering.

Fast math, the case started with .004" clearance, your firing pin shortened the case .005", that is .009". .009" is no go-gage length for some and beyond no go-gage length for others.

Again, I am the fan of cutting down on all that that case travel.

F. Guffey

[Brian Pfleuger]

Well this is no longer about chambering an AI gun, so....